1. Statement of the Technical Field
The invention concerns wireless communications networks and systems. More particularly, the invention concerns an anti-tamper method and apparatus for a communications link.
2. Description of the Related Art
Electronic security systems often rely on remote sensors which communicate data back to a central monitoring location. These systems generally make use of some type of communication link from the remote sensor to the central monitoring location. In recent years, wireless technologies have become more common for the purpose of implementing this communication link. However, with an evolution of data transport from wired to wireless, the potential for circumvention of such systems is increasing. In particular, the wireless data link presents an opportunity to interfere with, modify, or substitute bogus sensor data for actual sensor data. Many tamper protection methods exist to foil such activities. For example, some video surveillance systems utilize hardware and software configured to mark each frame of video data with a timestamp and/or a frame number. The video data with a timestamp and/or a frame number is transmitted wirelessly from a source communications device to a destination communications device. At the destination communications device, an anti-tamper check processing is performed on the video data. This processing involves determining a difference between a set of timestamps and/or frame numbers. Subsequently, a comparison is made between the difference value and a known threshold value. If the difference value is greater than the threshold value, the video data has been compromised.
Despite the tamper protection benefits provided by this method, it suffers from certain drawbacks. For example, an unauthorized individual can easily intercept a transmission of authentic video data and substitute bogus video data. For example, one or more frame time-stamps and/or frame numbers can be modified. As a result, modified and/or bogus data can be substituted for the authentic sensor data.
Another tamper protection method utilizes hardware and software configured to encrypt sensor data prior to its wireless transmission from a source communications device to a destination communications device. This method involves encrypting the sensor data based on an encryption key generated by a cryptographic device. However, it should be appreciated that such a cryptographic method may be computationally intensive, costly, and overkill for a particular user. For example, an encryption method can be unnecessary in surveillance applications where data integrity is important, but secrecy of the data is not. The computationally intensive proves of encrypting surveillance data can also decrease throughput of sensor data.
It will be appreciated that the tamper problem described herein is not limited to sensor applications. In fact, any data transported over any type of wireless link is subject to tampering, including unauthorized modification of the data, and/or substitution of bogus data. The data can include any type of payload data including audio data, video data, sensor data acquired by any type of sensor, and any other kind of data.
Despite the advantages of the known tamper protection methods, there is a need for a tamper protection method and system that offers a high level of signal integrity assurance at a physical layer without a decrease in sensor data throughput. There is also a need to ensure data integrity without a need to modify existing methods of transporting data. It is also desirable to provide a method for integrity verification of data that is undetectable except by sophisticated detection equipment and is difficult to jam.